In recent years, a demand for point-to-point (P-to-P) optical networks with a large capacity has been increased among data center companies. A large-capacity P-to-P optical network is provided using, for example, a wavelength division multiplexing (WDM) technique. In WDM transmissions, a plurality of optical paths with different wavelengths are multiplexed.
FIGS. 1A and 1B illustrate exemplary configurations of a WDM transmission system. In the example depicted in FIG. 1A, an arrayed waveguide (AWG) is provided at each site, and a plurality of transponders (TRs) are connected to each AWG. Each transponder accommodates a client or a router and transmits/receives an optical signal to/from a correspondent transponder at another site. Each transponder uses a different wavelength.
In the example depicted in FIG. 1B, a wavelength selection switch (WSS) is provided at each site, and a plurality of transponders (TRs) are connected to each WSS. As in the configuration depicted in FIG. 1A, each transponder accommodates a client or a router and transmits/receives an optical signal to/from a correspondent transponder at another site. Each transponder uses a different wavelength. However, the WDM transmission system illustrated in FIG. 1B includes an optical network controller. The optical network controller centrally manages the entirety of the network. For example, the optical network controller controls a wavelength used by each transponder and wavelength selection for the WSSs.
As a related technique, a technique has been proposed for facilitating addition or removal of a child device in a CWDM system in which communications are performed between a parent device and a plurality of child devices (e.g., Japanese Laid-open Patent Publication No. 2012-209818). An optical network control apparatus intended to enhance the efficiency of utilization of an optical frequency band has also been proposed (e.g., International Publication Pamphlet No. WO 2015/162874). In addition, related techniques are also described in Japanese Laid-open Patent Publication Nos. 2010-41444, 2008-54093, and 2007-124568.
In the configuration depicted in FIG. 1A, an available wavelength is determined for each port of the AWGs. Hence, when, for example, wavelength λ1 is allocated to a communication between clients x1 and y1, a transponder accommodating the client x1 and a transponder accommodating the client y1 each need to be connected to a port corresponding to wavelength λ1. Thus, in the configuration depicted in FIG. 1A, an optical path cannot be flexibly set or changed.
In the configuration depicted in FIG. 1B, an optical path can be flexibly set or changed. However, some users may desire a configuration that does not need to be provided with an optical network controller for centrally managing the entirety of a network.